Habitat change is the process of an environment being altered over a period of time, usually caused by human activity. The three main types of habitat change are habitat loss, habitat fragmentation, and habitat degradation. Habitat loss consists of land being converted for alternative land use, while habitat fragmentation is the division of habitats leading to increased edge effects and isolation. Habitat degradation can be defined as the slow reduction of a habitat’s ecological quality, usually caused by human activity such as pollution. When land is transformed during the process of habitat change, food, shelter, and water can become suddenly unavailable, making habitats often uninhabitable, forcing species to either adjust or die. This impacts species living in highly biodiverse environments, especially as they tend to be highly specialised, making it much harder for them to adjust to changes in their habitats.
Habitat loss can be seen in the phenomenon of coral bleaching. Set to become an increasingly major issue for marine ecosystems over the coming years, coral bleaching is the process by which coral expel their zooxanthellae algae as a result of exposure to high ocean temperatures. Between the coral and the zooxanthellae exists a symbiotic relationship by which the coral provides the algae with a protected environment, whilst the algae provide the coral with energy via photosynthesis. The expulsion of the zooxanthellae results in the coral losing its bright colours and turning white, hence the phrase coral bleaching. If temperatures stay too high for an extended period of time then there can be widespread coral loss, as seen in the Great Barrier Reef in 2017 were 50% of its coral was lost.
As a result of deforestation in the Amazonian rainforest for pastoral farming, habitats are becoming increasingly fragmented. This has led to its increased susceptibility to edge effects which change the composition of trees species at the edge of the habitat and therefore disturbing often highly specialised endemic species. In turn, this has massively decreased the biodiversity of the plant and animal species, as well as largely impacting the biodiversity and richness of the soil. This has consequently led to calls for deforestation patterns to maximise the edge to forest interior ratio through more circular shaped habitat fragments (see Figure 1).
Figure 1 – Diagram of edge to interior habitat ratio of different habitat shapes.
“Untitled”, 2003, Graphic, Christina Kennedy, Jessica Wilkinson and Jennifer Balch. Source: https://www.eli.org/sites/default/files/eli-pubs/d13-04.pdf
Biodiversity – The variety of flora and fauna species in an area/ecosystem (see An Introduction to Biodiversity article for more information)
Coral Bleaching – The process whereby the coral colonies lose their colour, due to the expulsion of microscopic algae (zooxanthellae) living in symbiosis with the coral
Edge effects – Changes in population or community structures that occur at the boundary of two or more habitats.
Endemic species – Plants or animals that exist in only one geographical area.